1. Field of the Invention
The present invention relates to a grade arithmetic unit in fuzzy inference and an input value sorter used in this grade arithmetic unit.
2. Description of the Related Art
When a conformity grade between a membership function and a fact is calculated in fuzzy inference using a MAX-MIN method, an input membership function showing the fact is generally compared by a minimum circuit with an antecedent portion membership function of a rule every discretization data and a smaller value of these membership functions is taken out. Thereafter, a maximum value of the membership functions is taken out and outputted as a conformity grade by a maximum circuit.
The conformity grade as an adaptation grade is calculated by using a fuzzy inferential circuit even when a fact input is provided as a determined value input. Namely, the determined value input is further set to a fuzzy input, or is used by enlarging this determined value input to a crisp set or aggregation.
Therefore, hardware for calculating the conformity grade is large-sized and there is naturally a limit of improvement of an accuracy in calculation of the conformity grade such as an accuracy in input and an accuracy in conformity grade. Further, it is necessary to provide a conformity grade in each of discrete positions of the antecedent portion membership function to this grade arithmetic unit. Accordingly, it is necessary to dispose a memory device for holding a large amount of data and a mechanism for reading these data from the memory device at a high speed.
In another example of the general grade arithmetic unit, minimum and maximum calculations are excluded by using a memory. For example, this general example is shown in Japanese Patent Application Laying Open (KOKAI) No. 2-159627. In this general example, a membership function name as a rule number is allocated to an upper address position and a discrete position of this membership function is allocated to a lower address position. A conformity grade is obtained from these address data by designating an input value and the membership function. In this general example, the conformity grade can be calculated at a high speed, but the memory has a large capacity. Accordingly, it is difficult to improve a processing accuracy such as an accuracy in input and an accuracy in conformity grade. Further, kinds of the membership function and the number of inputs thereof are limited.